Step-by-step electric motor



A. W. PLENSLER s'rEP-BY-STEP ELECTRIC uo'ion sept. 23, 1941. l

Eiled Feb. 17. 1945 if ja Jz lla.

Patented Sept. 23,1947

UNITED STATES PATENT OFFICE 'STEP-BY-STEP ELECTRIC MOTOR Alexander W. Plensler, Chicago, Ill., assignor, by

mesne assignments, to Belmont Radio Corporation, Chicago, lll., a corporation of Illinois Application February 17, 1945, Serial No. 578,458

7 Claims. 1

This invention relates to step-by-step electric motors and more particularly to such motors which are of the reversible type and which are exceptionally quiet in operation. I

Heretofore there have been proposed numerous types of step-by-step electric motors suitable for low-power applications where low cost is an important factor, particularly for applications where relatively low speed and high torque are required. Motors of this type generally have involved one or more electromagnets having reciprocable armatures. In one type the armature is connected to the driving pulley through a resilient cord-like element resulting in quiet operation but relatively low torque and power output. In another type the driving pulley is connected with a serrated or toothed disk and the armature is connected to rotate the disk through a resilient spring arm. This type of motor provides a relatively high torque and power output but is relatively noisy.

Further, in applications where itis necessary tokeep the cost of the motor to an absolute minimum, devices of the prior art have left something to be desired in the way of simplicity and It is an object of the invention, therefore, to provide a new and improved step-by-step electric motor which is effective' to overcome one or more of the disadvantages and limitations of the prior art motors of this type.

It is another object of the invention to provide a. new and improved step-by-step electric motor which is exceptionally quiet in operation and which is effective to develop a relatively high torque and power output. f

It is a further object of the invention to provide a new and improved step-by-step electric motor which is constructed of a minimum number of structural elements, which may be punchings or stampings.

In accordance with the invention, a. step-bystep .electric motor comprises a rotatable driven wheel having a resilient peripheral friction surface, electromagnetic means having a reciprocable armature and a driving arm connected to be actuated by the armature and having a driving shoe of substantial area in engagement with the friction surface of the wheel. In a preferred form of the motor, there are provided two electromagnets and associated armatures' and the driving arms act on opposite sides of the axis of rotation of the driving wheel and are thus effective to drive the wheel in opposite directions;

Further in accordance with the invention, a step-by-step electric motor comprises a pair of identical stamped side plates, a stamped bracket interconnecting and relatively supporting the side plates, and a driven wheel rotatably supported by and between the side plates. The motor alsoincludes .electromagnetic coil means supported by and between the side plates, at least one stamped armature for the electromagnetic means pivotally supported from the bracket, and a, driving arm connected to be actuated by the armature and having va driving engagement with the wheel.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, while its scope will be pointed out in the appended claims.

Referring now to the drawings, Fig. 1 is a view in front elevation, partly in section, of a, step-bystep motor embodying the invention; Fig. 2 is an end view and Fig. 3 a bottom view of the motor of Fig. 1; while Figs. 4 and 5 show details of the electromagnetic coil means of the motor and its mounting in the motor frame.

Referring now to the drawing, there is illustrated a reversible step-by-step electric motor embodying the invention and requiring, as structural members thereof, only four different stampings, a drive wheel and shaft, and a pair of driving arms. This motor comprises a pair of identical stamped side plates I0 and I I and a stamped U-shaped bracket I2 interconnecting and relatively supporting the side plates I0 and II, its side arms being secured thereto by rivets or machine screws I3 or equivalent. The motor also includes a driven wheel I4 having a resilient peripheral friction surface portion Ma of rubber or other resilient material and a shaft I5 therefor rotatably supported by and between the side plates I0 and II. Since the motor is inherently a low-speed motor, the shaft I5 may be disposed in aligned apertures in the plates I0 and I I serving as bearings for the shaft. The wheel I4 is provided with a hub Mb which may be secured to the shaft I6 by one or more set screws I4c.

The motor also includes electromagneticl coil l means, specifically a pair of electromagnets I6 and I l comprising laminated shell-type cores lia and Ila, respectively, the bottom arms of which are left open, as shown in Fig. 5. The cores Isa and I'Ia are'supported directly by and between the side plates I0 and II. For example, there are struck inwardly from the'side plates I0 and II lugs or ears'la.- Ina and IIa, lla which are disposed to grip the side arms of the magnetic core members lia and Ila, respectively. The striking of these lugs from the side plates I and II leaves windows therein, such as the window |011, and the cores are provided with extensions such as the extensions |89 which are proportioned to iit closely within the windows IIIb to hold the electromagnets securely in place. Ii' desired, the core extensions may be soldered to the edges of the windows in the side plates I0 and II, as indicated by the soldering of the extension ISg to the window I0b in Fig. 4.

The electromagnets I6 and I1 are provided with `a pair of identical stamped reciprocable armatures IBb, I1b, respectively, each being pivotally supported from the bracket I2 and operable upon energization of the electromagnets I6 and I1 to form with its respective core a substantially closed magnetic circuit therefor. To this endfthe inner ends of the armatures IBb, I1b areformed with three upturned prongs, the outer two' of which I6c, Ilc terminate in knife-edges or equivalent pivotal members which are seated in V-shaped indentations I2b, stamped in the lower face of the bracket I2. The central prongs I6d, IId of the armatures IGc, I1c, respectively, project upwardly through apertures I2c in the bracket I2 and are individually engaged by a pair of springs I8, I9 extending from a second stamped U-shaped bracket 2U interconnecting the side plates I0 and II, the arms thereof being secured to the side plates by way of rivets or screws 2 I, 2 I,

or equivalent. Thesprings I8 and I9 are disposed to bias the armatures ISb, Ilb, respectively, away from their respective electromagnets and to act in lines very near the pivotal axes of their respective armatures so that the armatures IBb, IIb are very sensitive to even slight energization of their respective electromagnets. Suitable connections I6e, I'Ic are made to the windings of the electromagnets I6 and I'I, respectively.

The motor also includes a pair of driving arms 22, 23, preferably formed of leaf-spring material, individually connected to be actuated by the armatures IBb, i'Ib. Specifically, the outer ends of the armatures I6b, I'lb are upturned as at I6f, IIf, respectively, and the arms 22 and 23 are secured thereto by rivets or screws 24, or the like. The driving arms 22, 23 have driving shoes 22a and 23a, respectively, of substantial area secured to their upper ends by soldering or otherwise and disposed in engagement with the friction surface I4a of the wheel I4, the arms 22 and 23 acting on the wheel I4 on opposite sides of its axis of rotation and therefore being effective when reciprocated to rotate the wheel I4 in opposite directions. If desired, guide rods 25 may extend between the side plates IU and II and be soldered or otherwise suitably connected thereto to prevent buckling of the resilient driving arms 22 and 23 during operation of themotor.

It is believed that the operation of the motor of the invention will be apparent from the foregoing description. In brief, energization of one of the electromagnets, for example electromagnet I6, by an alternating current, such as a commercial (iO-cycle alternating current, is effective to reciprocate its armature Ib against the bias of its spring I8, thereby reciprocating the driving arm 22. The shoe 22a engages the resilient portion I4a of the wheel I4 and gives it a force having a substantial tangential component which produces a step-by-step rotation of the wheel I4 in a clockwise direction, as viewed in Fig. 1. In

practice, the armature Ib does not return fully to its deenergized position shown in the drawings during each alternation oi the exciting current but partakes of a low-amplitude l-cycle oscillation in apparent continuous contact with the resilient frictional surface Ila of wheel I4, producing nearly continuous rotation thereof. Similarly, excitation of the electromagnet I1 produces rotation of the motor in the opposite direction.

The several features described cooperate to produce a reversible step-by-step motor of extreme simplicity and low cost and yet one developing a substantial power output at low speeds. As seen, the motor requires as structural members only four different stampings: (1) the identical side plates I0 and II, (2) the bracket I2,

(3) the bracket 20 and (4) the identical armatures IIib, I'Ib. In addition to these four structural elements, the motor comprises only the drive wheel and its shaft, the pair oi driving arms 22 and 23, the electromagnets I8 and Il and miscellaneous elements` such as the biasing springs I8, I9, screws, wires, etc. Therefore, the motor can be constructed in a minimum of assembly operations and from a minimum number of parts, at extremely low cost. At the same time, the knife-edge support of the reciprocable armatures IGb', I'Ib, the disposition of their biasing springs I8 and I9, respectively, and the substantially closed magnetic circuit of the electromagnets I6 and Il when energized impart to the motor a relatively high eillciency enabling it to develop a substantial power output at low speed. At the same time, the use of the driving wheel with the friction surface Ila and the cooperating driving shoes 22a, 23a reduces to a minimum the operational noise which is generally associated with this type of step-by-step motor, so that the motor is extremely quiet in operation.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be apparent to those skilled in the art that various changes and modiiications may be made therein without departing from the spirit or scope of the invention.

What is claimed as new is:

1. A step-by-step electric motor comprising, a rotatable driven wheel having a resilientl peripheral friction surface, electromagnetic means having a magnetic core and a reciprocable armature operable to form with said core a substantially closed magnetic circuit, and a driving arm connected to be actuated by said armature and having a driving shoe of substantial area in continuous engagement with said friction surface of said wheel during normal operation of the motor.

2. A reversible step-by-step electric motor comprising, a rotatable driven wheel having a resilient peripheral friction surface, electromagnetic means having a pair of magnetic cores and reciprocable armatures therefor operable to form with said cores substantially closed magnetic circuits, and a pair of driving arms individually connected to be actuated by said armatures, each of said arms having a driving shoe of substantial area in continuous engagement with saidfriction surface of said wheel during normal operation of the motor, said arms having lines of action on said wheel on opposite sides of its axis of rotation.

3. A step-by-step electric motor comprising, a rotatable driven wheel having a resilient peripheral friction surface, electromagnetic means having a magnetic core and a pivoted reciprocable armature operable to form with said core a substantially closed magnetic circuit, means for biasing said armature away from said means and disposed to actin a line near the pivotal axis of said armature, and a driving arm connected to be actuated by said amature and having a driving shoe of substantial area in continuous engagement with said friction surface of said wheel during normal operation of the motor.

4. A step-by-step electric motor comprising, a rotatable driven wheel having a resilient peripheral friction surface, electromagnetic vmeans having a magnetic core and a reciprocable armature operable to form with said core a substantially closed magnetic circuit, and a leaf-spring driving arm connected to be actuated by said armature and having a driving shoe of substantial area in continuous engagement with said friction surface of said wheel during normal operation of the motor.

5. A step-by-step electric motor comprising,- a pair of identical stamped side plates, a stamped bracket interconnecting and relatively supporting said side plates, a driven wheel rotatably supported by and between said side plates, electromagnetic coil means supported by and between said side plates, at least one stamped armature for said means pivotally supported from said bracket, and a driving arm connected to be actuated by said armature and having a driving engagement with said wheel.

6. A step-by-step electric motor requiring as structural members only four different stampings, a drive wheel and shaft, and one or more driving arms comprising, a pair o1' identical stamped 35 plates, a stamped bracket interconnecting and relatively supporting said side plates, a driven wheel rotatably supported by and between said side plates, a pair of electromagnets supported by and between said side plates, a pair ot identical stamped armatures for said electromagnets pivotally supported from said bracket, and a pair of driving arms individually connected to be actuated by said armatures, each oi.' said arms having a driving engagement with said wheel, said arms being effective to rotate said wheel in opposite directions.

ALEXANDER W. PLENSLER.

REFERENCES CITED The following references are of record in the file of this patent:

yUNITED STATES PATENTS Chubb Aug. 21, 1934 

